问题描述：
根据英语解释写出相应的单词
Someone who studies or works in biology .the force that cause something to fall to the ground or to be attracted to another planet .the typical weather conditions in a partieulcs area .very difficult to believe and therefore probably untrue .a thin paper cover in which you put and send a letter 共五句五个单词
Someone who studies or works in biology .the force that cause something to fall to the ground or to be attracted to another planet .the typical weather conditions in a partieulcs area .very difficult to believe and therefore probably untrue .a thin paper cover in which you put and send a letter 共五句五个单词
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